Clinical results have indicated that the era of successful therapeutic vaccination has arrived. Regression of lesions was shown for premalignant lesions caused by HPV and the clinical benefit of prolonged survival has been established. Vaccines based on synthetic long peptides are among the optimal vaccine platforms. Peptide vaccine or peptides-based vaccines are developed for the treatment of persistent infections and cancer, preferably targeting the immune system to clear cells that express viral antigens, cancer-antigens and/or neo-antigens. It is appreciated in the art that peptide-based vaccines capable of eliciting an effective cellular immune response (CD4+ and CD8+ T-cell response) targeting antigen-specific cytotoxic T cells capable of clearing the antigen-expressing cells. Antigens of choice include mutant sequences, selected cancer testis antigens and viral antigens (for review, see Melief et al. 2016 Journal of Clinical Investigation, Vol 125(9) pages 3401-3412).
One of the challenges of peptide-based vaccines is to provide for physically and chemically stable injectable solutions. This is in particular a challenge for peptide-based vaccine emulsions comprising more than one peptide and oil-based adjuvants. Injectable vaccine solutions are typically prepared on-site about 1 to 3 hours before administration to the patient using dried, mostly lyophilized peptides as a starting material. Therefore, there is a need for a suitable reconstitution composition that allows for the fast reconstitution of dried peptides, which can subsequently be admixed easily with oil-based adjuvants resulting in an emulsion that is physically and chemically stable for at least 2 to 3 hours storage at room temperature before being administered to the patient.